Earth boring drill and method



Feb. 26, 1935.

L. C. BLACK EARTH BORING DRILL AND METHOD Filed Sept. 5, 1933 2 Sheets-Sheet l FEE- Feb. 26, 1935. c. BLACK EARTH BORING DRILL AND METHOD Filed Sept. 5, 1935 2 Sheets-Sheet 2 Patented Feb. `2.6, 1935 UNITED STATES PATENT OFFICE y 10 Claims.

This invention relates generally to drills of the rotary type which are adapted particularly for the boring of earth wells, and to methods for utilizing the same.

It is an object of the invention to provide a drill of the above character which will afford a relatively high boring speed and relatively eil-lcient drilling action.

A further object of the invention is to provide an improved form of rotary drill which can .be used over relatively long periods of time without'the necessity of servicing, and in which the cutters can be readily replaced in the event they become broken or worn.

Another object of the invention is to provide a rotary drill which will have a relatively Wide range of application with respect to diiferent formations, and which when used upon soft formations, will drill at a rapid rate without becoming clogged.

Further objects of the invention will appear from the following description in which the prem ferred embodiment of the invention has been set forth in detail in conjunction with the accompanying drawings. Referring to the drawings:

Figure 1 is a side elevational view, partly in cross-section, illustrating a drill incorporating the present invention.I I

Fig. 2 isa cross sectional detail taken along the line 2-2 of Fig. 1.

Fig. 3 is a side elevational view illustrating collectively certain parts for the attachment of the cutters to their associated heads.

Fig. 4 is a cross sectional detail taken along the line 4-4 ei Fignl.

Fig. 5 is a plan view illustrating a formation pattern at the bottom of the well, such as is produced by the drill illustrated in the drawings.

Fig. 6 is a diagrammatic view illustrating the manner in which the cutters are brought into action upon the formation being drilled.

Referring rst to Figs. 1 and 2 of the drawings, the drill illustratedtherein consists of a shank 10, the upper end of which is threaded.

" as followsz-The lower portion 14vof the shank (Cl. Z55-71) 10 is enlarged somewhat and offset from the general axis of rotation 16 of the shank. The lower end face 17 of the portion 14 is finished along a plane arranged at an angle to the axis 16, the angle` as illustrated being about 221/2 degrees. Formed within the shank portion 14 there is a cylindrical counterbore 18, which serves to accommodate a. stud 19 formed upon the head 12.` To aiord a minimum amount of resistance to turningmovement between the head and the shank, and in order to lockthe head against removal, the stud 19 is shown provided with annular grooves 21, `which are alined with grooves 22 formed in the side walls of counterbore 18. Fitted within these grooves are the ball bearings 23, which are adapted to. be introduced into or removed from the grooves 21 and 22 thru side openings fitted .with removable plugs 24 and 25. preferably interposed between the lower face 17 of the shank, and the cooperating annular shoulder 29 formed upon the head 12., These thrust washers are preferably locked to shank 10 and to the head respectively, by means of keys 31 and. 32.

'I'he head 12, below the thrust shoulder 29, is formed to aiford a plurality of divergent legs 33, and it is to these legs that the cutters 13 are rotatably secured. I prefer that the cutters be of the disc type. Such cutters are characterized by peripheral cutting edges, and`by the fact that they are advanced against the formation in a drection generally laterally with respect to planes normal to their axes of rotation. Each of the cutters as illustrated consists of a body 34 formed of a metal or metal alloy having suitable hard ness and strength. The inner annular web portion 36 of this body cooperates with other elements to be presently explained, to form a suitable journal The periphery of the body is formed to ai ford an annular groove 37, which yserves to provide two spaced circumferential cutting edges 38 and 39. As will be presently made clear, the use of two spaced cutting edges is not essential to the invention, but is desirable and of considerable utility.

Theparticular form of connection illustrated between each of the cutters 13 and its associated leg 33, to form l'a suitable journal and to permit removal of the cutters for replacement and repair, incorporates the invention disclosed and claimed in my Patent No. 1,655,176. Briey this arrangement is as fol1ows:-Fitted upon the an-, nular web 36 there is an arcuate bushing 11,` the rear face of which is continued to form an Separate thrust washers 27 and 28 are also annular' washer 42. The lower end of the associated leg 33, has an integral projecting portion 43 provided with an arcuate groove 44 to receive bushing 41, and is also provided with a set back surface 46 in a plane coincident with the rear face of groove 44. Therefore when bushing 41 is within groove 44 as shown in Fig. 1, the Washer 42 engages surface 46. Extending thruthe leg 33, and somewhat excentric with respect to the axis of rotation of the cutter, there is a retaining bolt 47. This bolt passes thru an apertured lug 48, which is formed as a part of a crescent shaped retainer block 49. This block is provided with an arcuate recess 51to accomodate web 36,

and thus serves to complete the journal for the cutter togetherwith the bushing 41.

With respect to the positioning of the cutters 13 upon the head l2, in general the axes of rotation of the cutters should be inclined with respect to the axis of rotation of the head relative to the shank 10, rather than at right angles or parallel thereto. With the arrangement illustrated the general plane of each of the cutters, that is a plane taken normal to the axis of rotation of a cutter and medial of the body thereof, extends in a general direction outwardly from the axis of rotation of the head with respect to the shank, and at an angle thereto. That is, each cutter has a portion of its periphery extending downwardly toward the lbottoni of the Well and another portion of its periphery extending inwardly toward the axis of the head, so that each of the cutters has one of its side faces presented toward the direction of rotation of the head or drill. With the particular arrangement illustrated, which gives good results, the aforesaid general plane of each of the cutters 13 is at an angle of about 221/2 degrees with respect to the axis of rotation of the head about the shank.

In operating a drill of the type described above, it is desirable to circulate a suitable uid medium, such as the usual rotary drilling mud, downwardly thru the drill stem, to be discharged in a region adjacent the cutters 13. For this purpose the head 1 2 is shown provided with a central opening to accommodate a nipple or` pipe fitting 52. The upper end of this tting is.` attached to the shank, and is in communication with a passage 53 thru which mud can be forced from the drill stem. The lower end of pipe titting 52 terminates in a region generally surrounded by the cutters 13.

Before describing the manner in which my drill operates in practice, certain additional inherent characteristics may be pointed out. Assuming that the cutters have a positioning with respect to the head 12, and that the head l2 likewise has a positioning with respect to the shank, as specifically referred to above, with respect to an imaginary plane 54 the general planes of the cutters assume a denite angle of 22%". It will be noted that this plane 54 is taken normal to the axis of rotation of the head about the shank. With respect to a'horizontal plane 56, the general planes of the cutters assume various angles from a vertical position to an angle of maximum inclination, which in the aforesaid specic example is 45. If the head 12 is restrained against "rotary movement, but otherwise permitted to 70 move freely, and shank l is rotated about the axis 16, it is evident that a nutatory or wobbling movement will be imparted to the head and to the cutters. If finite restraints are placed upon movements of the cutters, both with respect to rotary movement about axis 16, and nutatory movements, (as in drilling operations) a torque component is impressed upon head l2, tending to rotate the head and cutters in the same direction of rotation, as that of the shank 1). In this connection it should be noted that during drillingA operations the shank (except fornormal advancing and retracting movements) cannot readily -move up and down in synchronism with nutatory movements of the head, because it is connected to the lower end of a relatively heavy drill stem. v

Assuming now that the drill is operating in a well with the cutters 13 against a bottom formation, and that the shank l0 is being continuously rotated about the general vertical axis of the Well, the restraints placed upon the cutters by virtue of contact with the formation, which restraints tend to oppose both rotary movements of the cutters about the vertical well axis and nutatory movements, the result is that head. 12 is caused to rotate continuously at a speed substantiallyl less than the rate of rotation of the shank, and that nutatory movement of the .head takes place to repeatedly impact the cutters upon the formation. In other words the head together with the cutters is caused to continuously wobble upon the formation and this Wobbling movement occurs together with rotational movement about the general vertical axis of the Well. At the same time,

with respect to the axis of rotation of the head about the shank, the cutters also revolve about their individual axes with respect to the head, so that fresh cutting surfaces are being continuously brought into contact with the formation.

Better understanding of the action described above can be had by reference to Figs. 5 and 6. Fig. 5 represents a typical formation pattern on the bottom of the well during operation of my drill. It will be noted that this pattern is not that of atorroid having its vaxis in a horizontal plane, but that valleys or pockets are formed separated by ridges. Thus in this case two similar pockets or valleys 1 are formed, which are separated by the central ridge 2. 'Ihe arrow in this figure indicates the direction of rotation of the shank with respect to the pattern being formed. Taking now a cross Isection along an imaginary cylinder 3, we have the development of Fig. 6, in which the action of the cutters upon the formation is also illustrated. The angle of attack of the cutters4 upon the formation for the upslopes a varies from a position in which both cutting edges are brought into contact with the formation, to a vertical position about half Way up the slope, and to a position of substantially one-half maximum inclination (e. g. 221/2) at the top of the slope. For the down slopes b, the inclination varies from half maximum value at the top of the slope, to maximum inclination value about half way down the slope, and then back to approximately7` one-half maximum inclination at the bottom of the down slope.

With a tool having three cutters substantially as illustrated in the drawings, it has been found that the ratio of rotation between the shank and thehead l2, is about 3 to 1, that is, the head is rotated one time for about three complete revolutions of the shank.v Therefore for each complete revolution of the shank, each cutter because tinuously upon the formation to produce a pattern such as illustrated in Figs. 5 and 6, but that the cutters act successively upon the formation, so that each cutter for only a part of its rise and plunge cycle is brought into contact with the formation. However cutting is not confined to a period when a cutter is plunged downwardly, but as indicated in Fig. 6, cutting may also occur during a rise.

The particular pattern produced upon the formation being drilled will of course vary in accordance with the particular design of drill utilized, and may also vary somewhat in accordance with the character of the formation acted upon.

For example with a drill utilizing four cutters in place of three, it has been found that three valleys are produced separated by three ridges, and there will be a higher ratio between the speed of rotation of the shank and that of the head. In

other words the number of valleys produced in trated, spaced apart in the direction of the axis Y,

of rotation of the cutter, is desirable for a reason which is evident from an inspection of Fig. 6. Duringoperation of a cutter upon the formation, both of its cutting edges are contacted with the formation simultaneously for only an instant. During other periods the cutting edges are in action separately, so that wear is distributed substantially equally between them. Such action makes for better penetration into the formation and vmore eiiicient cutting action, it extends the useful life of the cutter, and it makes possible a maximum amount of cutting surface with a minimum number of cutters, thus affording a maximum speed ratio between the shank and the head.

It is also evident that I may deviate somewhat from other structural details of the drill illustrated in the drawings. Thus although the particular angular positioning of the head with respect to the shank, and of the cutters with respect to the head, appear to be desirable as specified by way of example, deviations therefrom within the spirit of the invention are deemed feasible or may even be desirable dependent upon the conditions encountered.

I claim:

1. In a drill for boring wells, ashank adapted to rotate about the general vertical axis of the well, a head adjacent the lower end of the shank, said head being mounted upon said shank for rotation about an axis at an angle to the axis of said shank, and a plurality of circumferentially spaced cutters of! the disc type rotatably mounted upon said head, each of said cutters having one of its side faces presented toward the direction of rotation of said head.

2. In a drill for boring wells, a shank adapted to rotate about the general vertical axis of the well, a head adjacent the lower end of the shank, said head being mounted upon said shank for rotation about an axis at an angle to the laxis of said shank, and a plurality of circumferentially spaced cutters oi the disc type rotatably mounted upon said head, each of said cutters being positioned to have a portion of its periphery extending downwardly toward the bottom of the well l and another portion of its periphery extending 3. In a drill for boring wells, a shank adapted to rotate about the general vertical axis 'of the well, a head adjacent the lower end of the shank, said head being mounted upon said shankl for rotation about an axis at an angle to the axis of said shank, and a plurality of circumferentially spaced cutters of the disc type rotatably mounted upon said head, the central plane of each cutter making an acute angle with a plane through the axis of the head and passing through said cutter.

4. In a drill for boring wells, a shank adapted to rotate about the general vertical axis of the well, a head adjacent the lower end of the shank, said head being moimted upon said shank for rotation about an axis at an angle to the axis of said shank, and a plurality of 'circumferentially spaced cutters of the disc type rotatably mounted upon said head, the central plane of each cutterl being substantially parallel to the axis of said shank at one point during the rotation of said head.

5. In a drill for boring wells, a shank adapted to rotate about the general vertical axis of the well, a head adjacent the lower end of the shank, said head being mounted upon said shank for rotation about an axis at an angle to the axis of said shank,

and a plurality of circumferentially spaced cutters of -the disc type rotatablymounted upon said head, the axis of each cutter being substantially tangential, at one point during the rotation of the head, to a circle concentric to the axis of the shank.

6. In a rotary drill for boringv earth wells, a plurality of disc cutters carried by said drill and circlumferentially spaced from each other, said disc cutters being independently rotatable and mounted upon said drill so as to present a side face toward the direction of rotation of the drill,

and means for causing said cutters to progress about the axis of the well with rising and plunging movements.

7. In a rotary drill for boring earth wells, a plurality of disc cutters carried by said drill and circumferentially spaced from each other, said disc cutters being independently rotatable and mounted upon said drill so as to present a side face toward the direction of rotation of the drill, and means for causing said cutters to progress about the axis of the well with rising and plunging movements and for causing the edges of said cutters to engage theformation being cut at varying angles.

8. In a drill for boring wells, a shank adapted to rotate about the general vertical axis of the well, a head adjacent the lower end of the shank, said head being mounted upon said shank for rotation aboutan axis at an angle to the axis of said shank, and a plurality of circumferentially spaced cutters of the disc type rotatably mounted upon said head, the axis of each of said cutters being positioned in a plane which is parallel to the axis means for causing said cutters to progress vabout the axis of the well with rising and plunging movements, said disc cutters each having a. plurality of spaced peripheral cutting edges.

\10. In'a. rotary drill for boring earth wells, a

5 plurality of disc cutters carried by said drill .and

circumferentially spaced from each other, said disc cutters being independently rotatable and u mounted uponsaid drill so as to present a side face toward the direction of rotation of the drill, and means for causing said cutters to progress about the axis of the well with rising and plung-r ing movements and for causing the edges of said cutters to engage the formation being cut at vary-v ing angles, said disc cutters each having a plurality of spaced peripheral cutting edges.

- LESI'ER. C. BLACK. 

